In the art of surface grinding, solid abrasive wheels are increasingly being replaced by endless abrasive belts passing around cylindrical driving drums, and the belts are very effective for removing metal efficiently.
Where it is desired to produce a very flat surface of exact dimensions, however, in mass production of a number of identical objects for example, difficulty is encountered. In the movement of a succession of workpieces past an abrasive belt, certain portions across the width of the belt encounter metal for longer working intervals than others, and consequently are worn away more rapidly. Under such conditions the first fifty or so units may be flat within required tolerances, but thereafter the belt, while still usefully cutting metal, nevertheless produces a surface which increasingly departs from flatness with successive workpieces. Accordingly the belt must be replaced, even though it would still be capable of grinding perhaps 150 more pieces to a less exacting flatness tolerance.
The foregoing is true whether the work is fed past the abrasive belt linearly, or rotated and fed into the belt along the axis of rotation. While the situation can in some measure be alleviated by differently positioning successive workpieces for grinding, this repeated jigging adjustment is not consonant with efficient mass production.